1. Field of the Invention
This invention is directed toward wind driven power generating systems, and in particular, wind driven power generating systems useful for the production of power, such as electricity. In one embodiment, the present invention comprises an adjustable air scoop inlet section, an air turbine section of unique design, and an adjustable outlet section, which may include an adjustable drag curtain or outlet barrier for energy efficiency and system capacity considerations, to use the prevailing wind to produce power from the air turbine. The air turbine also utilizes a second phase of prevailing wind flowing through or around the outlet section to provide additional drive directly or indirectly to the turbine blades in a second stage of power production. The air turbine's exhaust flows into the outlet or exit section, which re-entrains the exhaust air into the downstream prevailing wind.
2. Description of Related Art
There have been a number of patent applications and issued patents which are related to wind power generating systems. The most common commercial methods to date have been turbines with blades that are directly driven by the wind without a collector or wind concentrator. Horizontal axis (i.e. axis of rotation is horizontal) turbines are probably the most common with vertical axis systems also being significant. These systems are simple, reasonably efficient, and commercially successful.
Wind power has surprisingly good economics and is capable of producing electricity at cost structure significantly less than 10 cents per kWh, commonly at 5-6 cents per kWh. Economics of wind power are constantly being studied and compared to existing methods of producing power which may be approximately 4 cents per kWh for large customers. This alternative energy production method has also been encouraged by tax incentives and special grants. There is now an expectation that each year increasing amounts of electricity will be generated by wind power, as well as other alternative energy based technologies.
Unfortunately, existing wind turbine designs have not been as widely adapted as is economically feasible. There are unforeseen problems with public reaction to the unsightly nature of the turbines and their visual dominance on a landscape, especially where there may be multiple installations of air turbines, often moving at different speeds and rotations with respect to each other, which may be viewed at the same time by a casual observer. There have been other issues. Existing wind turbines are often high off the ground, which increases maintenance costs due to poor accessibility. Some turbines have to reduce their operating speeds due to birds colliding with the turbine blades. There are infrastructure problems, where high voltage transmission lines are unavailable in favorable wind areas.
An example of a vertical axis turbine is described in U.S. Pat. No. 4,017,205 where a vertical turbine is integrated into a dome structure and the prevailing wind from any direction is meant to create an updraft. The goal is to create an upward force through a turbine which is useful for any wind direction. However, the practicality of the design is highly questionable. The air is not uniformly and forcibly directed through the generating turbine in a highly efficient and effective manner. The entrainment of the turbine exhaust air back into the wind is poorly thought out, and the lower directing surface would allow the turbine inlet air to flow easily around it horizontally without moving vertically.
Another example of the use of a vertical axis turbine is U.S. Pat. No. 4,309,146 where a vertical turbine is meant to be driven by a vertical airflow from a horizontal wind, which is directed upwardly by use of curved blades. An upper venturi creates a draft for the vertical air stream. The practical aspects of the design are highly limited. There is relatively little surface area where the wind is ‘caught’ and directed upwardly compared to the surface area of the power generating blades. The upper venturi, as illustrated, is poorly thought out from a flow re-entrainment and throughput standpoint as a large volume of horizontal wind is required to move a relatively small amount of vertical air. Moreover, as described in the previous paragraph, the vertical flow of air is not forced upwardly through the inner chamber. The draft is generated more from the venturi effect, which is known to be a weaker force. The airflow is more likely to move around the blades than be directed vertically.
Similar to the previously described patents, U.S. Pat. No. 4,365,929 discloses a vertical axis turbine that uses a building to ‘catch’ the wind and direct it vertically upward into the turbine. Various blades are installed on the building surface in a design attempt to force the air to flow upwardly into the turbine. The venturi design does not consider appropriate methods to re-entrain the turbine exhaust air back into the prevailing wind in an efficient manner, and the design is overly complicated. Additionally, as stated for previous patents, the air is not forcibly directed through the generating turbine, and the lower directing surface would allow the air to easily flow around it horizontally without moving vertically. As illustrated, the amount of surface area that is engaged with the prevailing wind compared to the complexity of the overall system is small. Also, the efficiency of the wind ‘catch’ and wind ‘discharge’ has not been carefully planned. Further, the building is a fixed size, and it is difficult to optimize the whole design when the wind ‘catch’ area is a constant size. Varying wind speeds require different surface ‘catch’ areas for efficient operation. It is less appealing to have the air intake close to the ground as the wind speed is lower.
U.S. Pat. No. 6,962,478 shows a vertical axis windmill that uses a unique outer wall with specially designed moving baffles to create a force on one side of the vertical rotating axis to cause rotation. However, the design of the air stream through the central opening of the framework and the closed baffles is inadequate. The surface area of the outer baffles far surpasses the ability of the framework to vent any air directed inside the framework.
U.S. Pat. No. 4,963,761 discloses a vertical axis fan turbine utilizing the prevailing wind to draw air upwardly through the turbine by a Bernoulli effect. As stated previously, a relatively large volume of air is needed to create the vacuum needed to draw a significant amount of air vertically, and the effect is not as efficient as other methods.
EP0003185 teaches the use of a large flexible canopy over a land area, such as a canyon, to create air movement through an air turbine. This design is not configured to catch a prevailing wind from any direction, and the simple structure is likely to be damaged in a high wind. The overly large design is meant to catch the movement of air from a thermal effect when the air is heated by the sun.
U.S. Pat. No. 4,116,581 discloses a windmill comprising a spherical structure that is divided into two hemispheres with the upper hemisphere rotating to catch the wind. One side of the upper hemisphere is cut away to direct the wind downwardly into the lower hemisphere and through a vertical axis air tube and turbine. An axial structure supports a shaft carrying a multi-bladed turbine of selected diameter centered in the air tube exit opening. The shaft is connected to a generator inside the axial structure. Only the air through the upper hemisphere provides power. No thought is given to providing a large exit space just after the turbine blades where the prevailing wind is allowed to enter and additionally generate power by rotating the turbine blades.
U.S. Pat. No. 993,120 discloses a vertical wind-mill which utilizes a vertical axis shaft, a casing having surface openings, a large cylinder with scoop-like vanes or blades mounted on a shaft, and the cylinder rotates to generate power. U.S. Pat. No. 4,017,204 describes wind motors which are propelled by the impact of the wind against the vanes of an impeller wheel, and wind channeling plates to gather the wind from a large area and funnel it at increased density and pressure to apply against the vanes. Again, in both of these patents no thought is given to providing a large exit space just after the turbine blades where the prevailing wind is allowed to enter and additionally generate power by rotating the turbine blades.
U.S. Pat. No. 6,952,058 discloses a wind energy conversion system, which includes upper and lower wind turbines having counter-rotating blade assemblies supported for rotation about a vertical rotation axis. A hood for supplying intake air to a wind turbine and an exhaust plenum for exhausting air from the wind turbine, with the hood and the exhaust plenum being directionally positioned is provided. U.S. Pat. No. 4,398,096 describes a wind-powered electric generator using a large opening/collector which routes the wind through an inner ducting and exhaust ducting in an “s” or “z” shaped flow. U.S. Pat. No. 4,516,907 discloses a wind collector with a side by side pair of power generators. None of these patents provide a large exit space just after the turbine blades where the prevailing wind is allowed to enter and additionally generate power by rotating the turbine blades.